Google now allows to hide the Badge, from the FAQ :
I'd like to hide the reCAPTCHA v3 badge. What is allowed?
You are allowed to hide the badge as long as you include the reCAPTCHA branding visibly in the user flow. Please include the following text: This site is protected by reCAPTCHA and the Google <a href="https://policies.google.com/privacy">Privacy Policy</a> and <a href="https://policies.google.com/terms">Terms of Service</a> apply.
For example:
So you can simply hide it using the following CSS :
.grecaptcha-badge {
visibility: hidden;
}
Do not use display: none;
as it appears to disable the spam checking (thanks @Zade)